Depends on the wattage of the power supply. In the past Apple Macbooks (before the Pro) were drawing too much power for AA seats to supply anything at all, as they'd trip the breaker.

The wattage is written on the power adapter. If it's over 75W there may be a problem. Though there is a post on Flyertalk that says the 787 and others have 225W shared between a pair of seats.

Power available regardless, on many airline seats the two prongs of many power supplies often barely connect or fall out. Buy a 6" three prong extension and you will find on many seats the three prong male plug will get a better connection with the seat and the new three prong jack will hold the (typically) two prong plug from the power supply more snugly. This is particularly for Apple MacBook Pros unless you use the overly long three prong cord Apple supplies.

The large-ish UK style 3 prong to American style adapters sometimes work fairly well but they tend to be so large there may be obstructions.